As is well known to those skilled in the art, it is difficult to satisfactorily cool hot gases, typically at temperatures as high as 1200.degree. F. or higher and particularly so when these gases contain particulates including ash and char. Typical of such gases may be a synthesis gas prepared as by incomplete combustion of a solid carbonaceous charge. The principal desired gas phase components of such a mixture may include carbon monoxide and hydrogen; and other gas phase components may be present including nitrogen, carbon dioxide, and inert gases. The synthesis gas so prepared is commonly found to include non-gaseous components including those identified as ash, which is predominantly inorganic, and char which is predominantly organic in nature and includes carbon.
These non-gaseous components are entrained or dispersed in the synthesis gas as solid or near solid particles typically having a particle size in the 1-10,000 micron range. The troublesome ash portions are typically of particle size less than 10-50 microns. At the temperature at which the synthesis gas is generated, usually 1800.degree. F.-3500.degree. F. several of the components of the ash are typically above their melting point and the ash may in fact be made up of a mixture of solid and molten fractions. The char component is also characterized by its viscous, near liquid, semimolten nature.
The presence of these particles, which pass through an undesirable viscous, sticky phase on cooling to lower temperature of typically 300.degree. F.-520.degree. F., introduces problems. As the particles are passed through the various conduits and coolers, the particles adhere to the surfaces with which they come into contact and in due course block the passageways through the cooler thereby rendering the cooler inoperative. Plugging of the various passageways through which the gas is to pass causes serious problems ranging from increase in pressure drop to complete blockage of the apparatus; in this latter instance, the possibility of damage to the apparatus is present due to undesirable increase in temperature and pressure. Even under the most favorable conditions, it would be undesirably necessary to shut down the apparatus for the purpose of cleaning out the deposits of the viscous and sticky solids.
It is an object of this invention to provide a novel process and apparatus for cooling a hot synthetis gas containing particles including ash and char which pass through an undesirable viscous, sticky phase on cooling through an intermediate temperature range.